I agree with Elder,
It all depends on what games at what resolution and quality settings you intend to play in the future. To play games such as, Far Cry 4 BF4, Fallout 4, etc smoothly at ultra settings 1080p, you need to spend over $1000 for a gaming PC. If you want a system that can be upgraded in the future with minimum costs, you need to pick a feature-rich motherboard that can run minimum 2 graphics card at full x16 speed. If I wanted to build a PC that can run most games at 1080p for next 3-5 years, I'd pick i7-5960x and 2x GTX 980 Ti in SLI for now which is way beyond your budget limit.
Anyway, lets get back to the topic. Below are my recommended parts for you.
http://www.reguluspc.com/custom-pc/1443255268.html
Processor: AMD FX-9370 - 4.4 GHz - 8 Core - 8MB L2 Cache - AM3+ $205
Mother Board: Gigabyte GA-990FXA-UD3 - AM3+ - AMD 990FX - SATA 6Gb/s - USB 3.0 $127
Cooling Fan: Cooler Master Hyper 212 EVO - CPU Cooler with 120mm PWM Fan (RR-212E-20PK-R2) $32
Power Supply: EVGA SuperNOVA 750B1 - ATX12V - 750W - 110-B1-0750-VR $72
Hard Drive: Western Digital Black 1TB - SATA 6Gb/s - 7200 RPM - 64 MB Cache - WD1003FZEX $72
SSD: Samsung 850 EVO 120GB 2.5-Inch SATA III - Seq. Read 540 MB/s - Write 520 MB/s $63
RAM: Corsair Vengeance Red 8GB (2x4GB) DDR3 1866MHz - CML8GX3M2A1866C9R $58
Graphics Card: MSI R9 380 GAMING 4G - 4GB GDDR5 - 2x DVI, 1x HDMI, 1x DP $240
Total Price $869